Control device for fixed point stop mechanism for sewing needle

ABSTRACT

The control device for fixed point stop mechanism employs several relays having a time delay element capable of putting a position detector which it to stop a sewing needle at a predetermined position in its active state only when required. When not required the position detector is put in inactive state by the relays.

United States Patent Kobayashi 1 May 30, 1972 [54] CONTROL DEVICE F OR FIXED POINT [56] References Cited STOP NECHANISM FOR SEWING UMTED STATES PATENTS NEEDLE 2,958,302 11/1960 Frankel et a1. ..112/219 A 1 lnvemofl Takanol'i Kobayashi, NagWa, Japan 3,590,969 7/1971 Kajitani et a1. ..1 121219 A x [73] Assignee: Mitsubishi Denki Kabushiki Kaisha,

Tokyo, Japan Primary Examiner-H. Hampton Hunter Filed: Nov. 4 1970 AttorneyRobert E. Burns and Emmanuel .l. Lobato [21] Appl. No.: 86,693 [57] ABSTRACT [30] Foreign Application Priority Data The control device for fixed point stop mechanism employs several relays having a time delay element capable of putting a Nov. 6, 1969 Japan ..44/889 88 998mm detector which it to p a Sewing needle at a predetermined position in its active stateonly when required. I When not required the position detector is put in inactive state [52] [1.8. CI. ..1 12/219 A by the relays [51] Int. Cl. ..D05b 69/22 [58] Field ofSearch ..112/219 A,219 3,219 R, 220, ZCIaims, lDrawing Figure OFF on R621 AB RA24 RA25 a 22, RA42 t 7| i 24 RA32 Z0 )8 32 3 Q 26 RA43 l BRAKE RA31 MECHANISM JRAZZ MOTOR RA1 RA2 IRA3 IRA4 Patented May 30, 1972 3,665,876

i on v oN RCEZJJAM M11 I 22 RA42 -52 -Ii l 24 o RA32 T 32 34 I L 26 Tf-L BRAKE "F M31 RA23 MECHANISM RA22 T MOTOR RA1 RA2 RAB RA4 I I 36 CONTROL DEVICE FOR FIXED POINT STOP MECHANISM FOR SEWING NEEDLE BACKGROUND OF THE INVENTION This invention relates to a control device for a fixed point stop mechanism for sewing needle comprising a clutch motor and a control circuit for stopping the needle of the sewing machine at a predetermined position.

A typical fixed point stop mechanism for sewing needle comprises a clutch motor having a mechanism capable of driving the sewing machine at either of a high speed for usual sewing operation or a low speed necessary for stopping the sewing needle at a predetermined position, detector means for detecting the position of the sewing needle, and means for stopping the operation of the sewing machine at a predetennined stop position as well as for changing the stop position of the sewing needle to another predetermined stop position.

According to the fixed point stop mechanism of this type, the main rotary shaft of the sewing machine has provided thereon a position detector comprising a circuit nonconductive when the sewing needle reaches to the predetermined stop position and conductive when the sewing needle is not in the predetermined position. The conductive and nonconductive modes of operation of the position detector is utilized to control the drive or stop of the low speed driving mechanism, thereby to accomplish the fixed point stop operation of the sewing needle.

With the arrangement as above outlined, however, there have been several disadvantages.

One of them is an overrunning of the sewing machine which causes the machine to make a few rotations even after the sewing needle has reached to the predetermined position where the sewing needle is to stop. This is because, since the position detector is composed of an electrically conductive rotatory drum having an insulating segment thereon and at least one brush brought in contact with the periphery of the rotatory drum to break the electrical contact therebetween when the insulating segment on the drum is brought in contact with the brush, thereby to detect the position of the sewing needle, if the braking and stopping operation is not completed when the brush is electrically isolated from the rotatory drum by the insulating segment, the brush is again brought in contact with the drum to bring the position detector into its conductive state. This causes the low speed driving mechanism to be energized, resulting in a rotation of the sewing machine.

Besides, in the event that the operator turns the pulley of the stopped sewing machine by his hand according to the custum established during using an old fashioned sewing machine having no usual fixed point stop mechanism, the drum of the position detector is rotated to turn the position detector from its nonconductive state to its conductive stste. This leads the sewing machine to suddenly rotate, which is extremely dengerous for the operator.

In addition, since the position detector has generally been mounted to the pulley which is apt to be operated by the operators hand, there has been a fear that the operators hand may touch the electric circuit of the position detector, resulting in receiption of an electric shock.

Further, upon sewing, the sewing needle is often required to be able to switch its stop position between two positions the upper most and the lower most stop positions at operator's will. To this end, the conventional control device has been arranged such that the detection of the position of the needle in terms of a first stop position can be accomplished when the foot pedal is positioned in its neutral underpressed position or original position, and the detection of the position of the needle in terms of a second stop position can be accomplished when the foot pedal is depressed by the operators heel. With the circuit arrangement of the conventional control device, however, after the above-mentioned switching operation has been completed, the foot pedal has inevitably passed through its neutral position when its position is to changed from the position depressed by the operators heel to the position depressed by the operator's toe at which the sewing machine is operated at the usual high speed. Therefore, when the foot pedal returns to its neutral position, the position detector returns to its original state. This results in a superfluous and, in some cases, harmfull movement of the sewing machine because the sewing machine rotates by half from the second stop position to the first'stop position.

SUMMARY OF THE INVENTION Accordingly, an object of the invention is to provide a control device for a fixed point stop mechanism comprising a position detector circuit which is operative only during the fixed point stop operation and inoperative during it is not required, thereby to remove the above-mentioned disadvantages of the conventional control device such as overrunning of the sewing machine, a sudden movement of the sewing machine due to the operator's manual operation of the pulley, a fear of an electric shock, and a superfluous and harmfull movement of the sewing machine upon changing the stop position of the needle.

Another object of the invention is to provide a new and improved control device for fixed point stop mechanism for sewing needle capable of performing a complete fixed point stop operation with the disadvantageous operations of the sewing machine eliminated.

BRIEF DESCRIPTION OF THE DRAWING The invention will become more readily apparent from the follwoing detailed description taken in conjunction with the accompanying single drawing which shows a circuit diagram of the control device for fixed point stop mechanism for sewing needle constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing wherein one embodiment of the invention is illustrated, the control circuit comprises an electric source 10 connected to a switch 81. Although not illustrated, the switch S1 is linked to a foot pedal of the sewing mechine or to a clutch lever for the clutch motor so as to be brought into its ON state as illustrated by a dash line in the FIGURE when the foot pedal is depressed by the operator's toe or the clutch is connected to each other to drive the sewing machine at a high speed for usual sewing operation. When the foot pedal is released to be returned to its neutral inoperative position or the clutch is disengaged, the switch S1 is brought into its OFF state as illustrated by a solid line in the FlGURE.

The switch S1 is connected at one of its contacts to a relay RA! which is energized by the source 10 while the sewing machine is driven at a high speed or while the switch S1 is in its 0N state. When the switch S1 turns into the OFF state due to the returning of the foot pedal to its original position, the relay M1 is deenergized after a very short time of delay because of an OF F-retarding circuit composed of a resistor 12 and a capacitor 14.

It is also seen that the control device comprises a position detector generally designated by the reference numeral 16. The position detector 16 is of the conventional design and serves to detect the position of the sewing needle (not shown) which is to be stopped at a predetermined fixed point. The position detector 16 comprises an electrically conductive rotatory drum l8 fixed to the main rotary shaft of the sewing machine and having formed an insulating segment 20 on one portion of its circumference, a first brush 22 which serves to detect the lower position of the sewing needle, a second brush 24 for detecting the upper position of the sewing needle, and a third or common brush 26 capable of always maintaining an electrical contact between the same and the rotatory drum 18. Therefore, when the rotatory drum 18 is positioned as illustrated in the Figure, the second brush 24 and the common brush 26 are electrically connected through the rotatory drum 18, while the first brush 22 is electrically isolated from the common brush 26 because of the presence of the insulating segment 20.

In order to control a low speed driving mechanism and a brake mechanism (not shown) necessary for performing the fixed point stop operation, there is provided a relay RA2 operative in response to the ON or OFF state of the position detector 16. A contact RA41 is for a relay RA4 which will be described later in detail and comprises a backand a fore-contacts for switching the position detector circuit so as to be able to change the stop position of the sewing needle. The backcontact of the contact RA41 is connected to the first brush 22 through a fore-contact RA21 which turns ON when the relay RA2 is energized, and the fore-contact is directly connected to the second brush 24. The common brush 26 of the position detector 26 is connected to the relay RA2 through a contact RA22 similar to those previously described and a back-contact RA31 connected in parallel with the contact RA22. The contact RA31 turns OFF when a relay RA3 which will be described later in detail is energized.

A fore-contact RAll of the relay RAl is provided bridging in parallel with the various circuit elements including from the contact RA4] to the common brush 26.

In order to change the stop position of the sewing needle from the predetermined position to the other predetermined position at operators will, a switch S2 which may be disposed to the foot pedal so as to be turned ON when the foot pedal is depressed by the operators heel is inserted between the source and a relay RA4. The relay RA4 is energized when the switch is brought in the ON state. In order to ensure that the relay RA4 is energized only after either of the upper or the lower stop position (in this embodiment, the lower stop position) has been detected, a back-contact RA23 is connected between the switch S2 and the relay RA4. In addition, in order not to allow the relay RA4 to be deenergized once it has been energized by the electric source 10 even when the relay RA2 is energized through the contact RA41 to turn OFF the contact RA23, a contact RA43 of self-holding type is connected in parallel with the contact RA23. When the relay RA4 is energized, the relay RA3 is brought into its ON state by the contact RA42 with a short delay derived from an ON-detarding circuit composed of a resistor 28 and a capacitor 30. In order to maintain the relay RA3 in its energized state even after the contact RA42 has been turned into OFF state, a contact RA32 of self-holding type is connected in parallel with the contact RA42.

It is also seen that the control circuit of the invention further comprises another circuit composed of an electric source 32 for energizing a brake mechanism 34 and a low speed driving motor 36 for performing the fixed point stop operation. The brake mechanism 34 and the low speed driving motor 36 sre controlled by a fore-contact RAZS of the relay RA2 and a back-contact RA24 of the relay RA2 respectively.

The operation of the control circuit for fixed point stop mechanism of the present invention will now be described.

It is now assumed that, in order to perform the usual sewing operation, the operator depresses the foot pedal by his toe and the sewing machine is driven at a high speed by the clutch motor. Under these conditions, the switch S1 is in its ON state as shown by the dash line in the Figure, the relay RAl is energized, the capacitor 14 is charged, and the contact RAl 1 turns ON. Therefore, the other circuit including the position detector 16 is electrically isolated from the source 10.

After the sewing operation has been finished, the foot pedal is released to be returned to its original neutral position. At this time the switch S1 turns OFF as shown by the solid line in the FIGURE to cut off the circuit including the relay RAl. Simultaneously, the circuit including the position detector 16 is connected to the electric source 10. It is to be noted, however, that even after the relay has been deenergized, the relay RAll remains in its ON state for a while owing to the discharge from the capacitor 14, resulting in continuation of the energization of the relay RA2 through the contact RAM and the contact RA31. Then, the contacts RA21, RA22 and RA25 are brought into the ON states to connect the position detector 16 to the source 10. At the same time, the driving motor 36 begines to drive the sewing machine at the low speed, decelerating the machine until its predetermined low speed. When the capacitor 14 terminates its discharging and the contact RAll turns OFF, the position detector 16 begines to detect the position of the sewing needle.

Under these circumstances, at the time that the sewing needle reaches to the predetermined lower most position, the electrical contact between the first brush 22 and the drum 18 is broken because the insulating segment 20 is interposed therebetween, thereby to deenergize the relay RA2. This causes the contacts RA21, RA22 and RAZS to be brought into the OFF states and the contacts RA23 and RA24 to be brought into the ON states. Therefore, the low speed driving motor 36 stops its operation, and the brake mechanism 34 applies itsbraking action to the sewing machine to stop the same at its predetermined position.

With the arrangement as above described, an overrunning of the sewing machine which has often took place with the conventional control circuit never takes place. This is because, even if the stop and braking operation is not accomplished during the brush 22 is in contact with the insulating segment 20 alone and the electric path between the brush 22 and the brush 26 is established, the relay RA2 is never energized because its self-holding contact RA21 remains in its OFF state.

To change the stop position of the sewing needle from its lower position to its upper position, the foot pedal is depressed by the operators heel to turn ON the switch S2. Then the relay RA4 is energized and the contacts RA41, RA42 and RA43 are brought into the ON states. It is to be noted that the relay RA4 is energized only after the position detector 16 has detected the lower position of the needle even when the operator turns on the switch S2 before the sewing needle reaches to the lower position because of the presence of the contact RA23 of the relay RA2.

When the contact RA41 turns on, the circuit for detecting the lower position of the needle including the first brush 22 is cut off and the circuit for detecting the upper position of the needle including the second brush 24 is connected to the source 10. Then, the relay RA2 is energized through the electrical path including the back-contact of the contact RA41, the second brush 24, the third bursh 26 and the contact RA31. As a result, the low speed driving motor 36 is driven to drive the sewing machine to change the position of the sewing nee dle from the lower stop position to the upper stop position. Although the contact RA23 turns ofi'at this time,,the relay RA4 is held in its energized state because of the contact RA43 which remains in its ON state. It is to be noted that, although the relay RA3 is connected to the source 10 when the relay RA4 is energized through the contact RA42, it is only after the capacitor 30 has been charged to a certain extent that the relay RA3 begines to be energized. In other words, the capacitor 30 is so designed that the relay RA3 is energized immediately after the relay RA2 is energized again. This causes the contact RA31 to turn into the OFF state.

After the sewing needle has reached to the predetermined upper position, the insulating segment 20 on the rotatory drum 18 comes in contact with the second brush 24 to cut off the electrical path between the second brush 24 and the common bnish 26. This causes the relay RA2 to be deenergized again, and the contacts RA21 to RA25 inclusive are operated to deenergize the low speed driving motor 36, and the sewing machine is stopped by the operation of the brake mechanism 34.

It is easily understood that, as similar to the previous case, even if the sewing machine is not stopped at the position where the brush 24 is electrically isolated from the drum 18, the relay RA2 is never energized because the contacts RA22 and RA31 are in their OFF states. This ensures the fixed point stop operation of the sewing machine to be accomplished without a fear of overrunning which was often took place with the sewing machine having the conventional control device for the fixed point stop mechanism.

After the fixed point stop operation has been completed, the foot pedal is released to return to its original neutral position. Therefore, the switch S2 turns OFF to deenergize the relay RA4 and the contact RA4] turns into its OFF state, resulting in reset of the position detector circuit in its initial position or the position capable of detecting the first stop position of the sewing needle.

It is to be noted that, at this time, the contacts RA21, RA22 and RA31 are in their OFF states and the relay RA2 is not energized. Therefore, the control device of the present invention is free from the disadvantages which have been seen in the conventional device such as superfluous rotation of the sewing machine and returning of the sewing needle to the second position again. ln addition, for preventing these disadvantages, the control device is not required to have an additional device.

It is also to be noted that, after the desired operation has been completed, the sewing machine never runs even if the pulley of the machine is rotated by the operators hand and the position detector 16 is brought in its every possible positions,

F ruther, since the positive and negative sides of the position detector 16 are cut off by the contacts RA4! and RA21 and the contacts RA22 and RA31 respectively to electrically isolate the position detector 16 from the electric source 10, the operator can never receive the electric shock even when he touches the position detector 16.

in order to operate the sewing machine at the high speed for performing the usual sewing operation again, the switch S1 is turned into ON state by depressing the foot pedal by his toe as in the previous case. Then, the relay RA3 is deenergized, and the contact RA31 turns ON resulting in a quite identical mode of operation of the circuit to that previously described.

As has been described, according to the invention the position detector circuit is put in its active state only when it is required to perform the fixed point stop operation and cut off when it is not required. This arrangement leads to an extremely stable operation of the device and a high safety for the operator, exhibiting several advantages in practical use.

What we claim is:

l. A control device for fixed point stop mechanism for sewing needle comprising position detector means capable of detecting the position of a sewing needle, first relay means having a contact for shortcircuiting said position detector means, said first relay means being energized by a source of electric power during usual sewing operation of the sewing machine and capable of maintaining said energized state for a predetermined period of time even after said energization by the source of electric power has been terminated, second relay means having a contact connected in series to said position detector means and operable in response to the operation of said position detector means, third relay means capable of changing the set position of said position detector to enable said sewing needle to stop at another predetermined position, and fourth relay means having a contact connected in parallel with the contact of said second relay means, the contact of said fourth relay means being closed at least upon the begining of the operation of said position detector.

2. A control device for fixed point stop mechanism for sewing needle comprising position detector means having a first and a second position detector circuit capable of detecting the position of a sewing needle, first relay means energized by a source of electric power during usual sewing operation of the sewing machine, time delay means for maintaining the energized state of said first relay means for a predetermined period of time even after said energization by the source of electric power of said first relay means has been terminated, a contact for said first relay means disposed in parallel with said position detector means and closed during said first relay means is energized to shortcircuit said position detector means, a first contact for said second relay means connected in series to said first or second position detector circuit of said positron detector, a second contact for said second relay means connected in series to said position detector, third relay means energized in response to the operators operation, a contact for said third relay means for switching said position detector means from its first or second position detector circuit to its second or first position detector circuit upon the energization of said third relay means, fourth relay means having a contact connected in parallel with said second contact for said second relay means and being closed at least upon the beginning of the operation of said position detector means. 

1. A control device for fixed point stop mechanism for sewing needle comprising position detector means capable of detecting the position of a sewing needle, first relay means having a contact for shortcircuiting said position detector means, said first relay means being energized by a source of electric power during usual sewing operation of the sewing machine and capable of maintaining said energized state for a predetermined period of time even after said energization by the source of electric power has been terminated, second relay means having a contact connected in series to said position detector means and operable in response to the operation of said position detector means, third relay means capable of changing the set position of said position detector to enable said sewing needle to stop at another predetermined position, and fourth relay means having a contact connected in parallel with the contact of said second relay means, the contact of said fourth relay means being closed at least upon the begining of the operation of said position detector.
 2. A control device for fixed point stop mechanism for sewing needle comprising position detector means having a first and a second position detector circuit capable of detecting the position of a sewing needle, first relay means energized by a source of electric power during usual sewing operation of the sewing machine, time delay means for maintaining the energized state of said first relay means for a predetermined period of time even after said energization by the source of electric power of said first relay means has been terminated, a contact for said first relay means disposed in parallel with said position detector means and closed during said first relay means is energized to shortcircuit said position detector means, a first contact for said second relay means connected in series to said first or second position detector circuit of said position detector, a second contact for said second relay means connected in series to said position detector, third relay means energized in response to the operator''s operation, a contact for said third relay means for switching said position detector means from its first or second position detector circuit to its second or first position detector circuit upon the energization of said third relay means, fourth relay means having a contact connected in parallel with said second contact for said second relay means and being closed at least upon the beginning of the operation of said position detector means. 